Carpal tunnel syndrome is often caused by a combination of factors that may include hereditary predisposition, injury, repetitive use and work stress. The median nerve runs from the forearm into the palm of the hand. When it is squeezed at the wrist, pain, weakness and numbness may result in the hand, wrist and arm. The carpal tunnel is the narrow passage at the base of the hand that houses the median nerve; thickening of irritated tendons or swelling can narrow the tunnel and squeeze the nerve.